RV-7 Oil cooler question - Page 2

Radomir · #11 03-11-2010, 01:17 PM

Mags or Electronic Ignition?

Do you run ROP, at peak, or LOP?

Is the engine broken in? (how many hours)

Have you tried running it LOP yet? I'd expect a significant drop in temps (both oil temp and CHTs)

Just lookin' at some photos from a recent trip... at 10,500.. OAT 34 degrees... oil temp 168... highest CHT 330 (lowest 310)... This is with a firewall-mounted SW 8406R...

ghatch · #12 03-11-2010, 05:55 PM

Hi Darwin,

Check you PMs

Gerry

ghatch · #13 03-11-2010, 05:57 PM

All flight have been rich of peak. There was about 45hr on engine when previous temps were measured. I have not run LOP because I haven't done a GAMI spread check(s)

Gerry

L.Adamson · #14 03-11-2010, 08:34 PM

Quote:

Originally Posted by 647jc

My undestanding is that even when the vernatherm is closed, a small amount of oil is still allowed to flow through the oil cooler. This is to prevent oil from congealing in the cooler and causing a total blockage. The Lycoming manual does not really quantify the amount of oil that flows to the cooler when the vernatherm is closed other than saying a small amount. So, the effect of blocking air flow through the cooler to increase oil temps is really difficult to quantify. My experience is that unless oil temperature is warm enough to cause the vernatherm to open significantly, blocking off air flow through the cooler will have little effect increasing oil temperature.

I do have the Van's cooler shutter. It needs to be mounted in front of the cooler, and it works very well. Mine is cable operated from the cockpit.
I installed this last fall, after getting tired of taping the cooler front with metal duct tape for winter months.

L.Adamson -- RV6A

ghatch · #15 03-12-2010, 05:50 AM

What hose size are you guys using to and from the oil cooler? -8 or -6 ?

Gerry

DanH · #16 03-12-2010, 07:29 AM

Quote:

Originally Posted by ghatch

What hose size are you guys using to and from the oil cooler? -8 or -6 ?Gerry

Now there's an interesting technical issue to explore.

As David said....the vernatherm is retracted and the oil cooler bypass port is open when the oil is cold. Oil flows through the cooler AND through the bypass. The vernatherm extends as the oil gets warmer, eventually closing the bypass port and forcing all flow through the cooler. Extends hot, shrinks cold....guys should be able to remember this familiar principle

The system is driven with a positive displacement pump. With the oil hot and bypass closed, the only available path is through the cooler and hoses......and hose size should make no difference. Both the -6 and the -8 hose should flow the same volume of oil because a positive displacement system doesn't allow it to be any other way. The smaller -6 will result in higher oil velocity in the hose and higher pressure between the pump outlet and the cooler return fitting.

Things get interesting with the oil cold. Remember, the vernatherm is open so the oil can flow through both the cooler and the bypass. The volume split will be in proportion to flow resistance in each path. In theory, a smaller hose should result in less flow through the cooler and more through the cooler bypass, making the -6 a better choice for cold weather operations.

So, theory seems to suggest the -6 is a better choice; same oil volume through the cooler with oil hot and vernatherm closed, less volume through the cooler with oil cold and verntherm open.

Is it really the better choice? Darned if I know. Practical details can trip up a good theory. For example, right angle fittings could be a larger potential problem with -6 oil plumbing; the velocity increase could make them more prone to cavitation. More theory really, but all fun to think about.

David-aviator · #17 03-12-2010, 08:10 AM

I do believe the standard is -8 hose for oil plumbing with a Lycoming. Whether or not -6 matters I don't know but it would seem logical if what Dan says is true, -4 would work also. But it is not done. This has been discussed before but I don't think anyone has gone to the trouble to prove it.

Dash 8 works, why not stick with it? If Gerald is running with -6, change it to -8, maybe it will make a measurable difference.

ghatch · #18 03-12-2010, 03:42 PM

Thanks guys for your responses. I have decided to go with a SW-10599R cooler mounted on the plenum behind cylinder 4 with an offset of 1/4" behind the plenum away form the cylinder fins to allow more air to get to the oil cooler fins. I will use 45 deg -8 fittings. It will be a tight fit. As previously stated, any pictures of your setup will be appreciated.

Gerry

Bubblehead · #19 03-12-2010, 04:06 PM

Quote:

Originally Posted by DanH

Now there's an interesting technical issue to explore.

The system is driven with a positive displacement pump.

Careful Dan. Someone will be on here talking about filling up his swimming pool again! I wouldn't mind but he has not paid me the 6-pack of Shiner from the last time!

L.Adamson · #20 03-12-2010, 05:29 PM

Quote:

Originally Posted by L.Adamson

I do have the Van's cooler shutter. It needs to be mounted in front of the cooler, and it works very well. Mine is cable operated from the cockpit.
I installed this last fall, after getting tired of taping the cooler front with metal duct tape for winter months.

Today............. Van's cooler shutter temps, fully shut. Outside temps 29-34 F. at 10,500' msl. Oil temps from 190 to 195, and 212 in a climb.